The invention relates to the use of bicyclo[3.3.0]octane derivatives as plasticisers or solvents for polymers. including thermoplastics.
Plasticisers are indispensable components for thermoplastic materials such as poly(vinyl chloride), and other polymer systems. The most commonly used plasticisers are diesters of dicarboxylic acids, among which the phthalic acid diesters are frontrunners in the plasticiser market with 89%, about half of which is made up of the isomeric diisooctyl esters. Whilst the existing plasticisers are generally satisfactory, there is a need for the range of plasticisers to be extended. Moreover. the existing plasticisers are virtually without exception based on petroleum products, whereas it is desirable for these to be replaced. as far as possible, by renewable raw materials. From an environmental and health point of view it is likewise desirable for dialkyl phthalates to be replaced.
Polyesters based on isosorbide and dicarboxylic acids (adipic acid, suberic acid, sebacic acid and dodecanedioic acid) having molecular weights above 10,000 have been suggested by Braun and Bergmann (Angew. Makromol. Chem. 199 (1992), 191-205) as plasticisers for PVC. JP-A-8-173788 describes the use of fatty acid diesters of sorbitans and isosorbide as an emulsifier. JP-A-59-175408 discloses the cosmetic use of esters of isosorbide with fatty acids having more than 8 carbon atoms. WO 96/33689 describes the use of a plasticising solvent, including dimethyl isosorbide, in film-forming water-in-oil emulsions for use in cosmetics.
We have now found that esters and ethers based on isosorbide and analogous derivatives having a low molecular weight have excellent characteristics as plasticisers and solvents for polymer materials. The derivatives are defined in the appended claims. The central unit of these derivatives is a bicyclo[3.3.0]octane-4,8-diyl system, whose carbon atoms in the 2- and 6- position may be replaced by a heteroatom, such as sulphur and in particular oxygen. The attachment of side chains in the 4- and 8- positions can take the form of an ether, ester, (thio)carbonate. thioether, thioester, amide, (thio)-urethane, urea, phosphate or phosphonate. Esters are preferred, but carbonates, urethanes and especially ethers can also advantageously be used. Phosphates and phosphonates are preferred when in addition to the plasticising effect a flame retardant effect is desired.
The side chains thus attached are preferably medium-length alkyl groups. Medium length means at least 3 carbon atoms. preferably at least 4 carbon atoms, especially (for ethers) at least 6 carbon atoms, up to 10 or even 12 carbon atoms. Where reference is made to alkyl, alkenyl etc., these terms include both linear and branched groups. depending on the particular use. branched groups, e.g. isobutyl, isooctyl, isononyl, 2-ethylhexyl and the corresponding acyl groups, or unbranched groups may be preferred. Examples of suitable alkanoyl groups include butanoyl, hexanoyl, 2-ethyl-hexanoyl, octanoyl, decanoyl, and unsaturated groups such as benz(o)yl and undecenoyl. Mixtures of alkyl groups are suitable as well, their average chain length is preferably C4-C12.
It is also possible for oligoester side groups of a diacid and a diol, for example succinic acid, which may or may not be substituted. and isosorbide, or of a hydroxy acid such as hydroxystearic acid or caprolactone, to be attached, with an alkyl or alkanoyl group as the terminal group. The chain length of such oligomeric side groups is 1-20, preferably 1-10, most preferably 1-5 repeating units on either side of the central unit, with molecular weights preferably between about 600 and 2000.
The derivatives according to the invention can be prepared in a manner known per se. Derivatives where X represents an oxygen atom in formula 1 can be prepared starting from isosorbide or the isomeric dianhydrohexitols such as isomannide and isoidide. The dianhydrohexitols can in turn be obtained from the corresponding monosaccharides (glucose, mannose) and di- and polysaccharides (sucrose, maltose, lactose, starch, cellulose, galactomannans and the like). Derivatives where one of the atoms X is a nitrogen or a sulphur atom can be prepared in a similar manner from a suitable amino or thio sugar. Derivatives where both atoms X are sulphur atoms can be prepared starting from 1,4-dithiapentalen-3-one which, by reduction and addition, can be converted into a 4,8-disubstituted 2,6-dithiabicyclooctane. Derivatives where one of the groups Y contains a nitrogen or sulphur atom can be obtained from the corresponding 2-amino- or 2-thio sugars, such as a hydrolysis product of chitin. The side chains can be introduced by esterification (eg. using a reactive carboxylic acid derivative), etherification, isocyanate addition, and the like. Polyester side groups can be introduced in a manner known per se, by polycondensation of the suitable dicarboxylic acids and diols or hydroxy acids.
The derivatives according to the invention can be worked into polymer materials in a manner known per se. In general, the polymer and the plasticiser can be mixed in a ratio of between 100:1 and 1:9. The ratio is preferably from 10:1 to 10:8. In addition to the plasticisers or plasticising solvents according to the invention, other customary components are used such as stabilisers, flow improvers, pigments, antioxidants, UV absorbers, flame retardants. fillers, oligomeric or polymeric resins or varnishes, reactive monomers, activators, starters, desiccants, lubricants, waxes. solvents, biocides and the like. This may involve, for example, organic compounds of calcium. magnesium, zinc or barium, xcex2-diketo compounds, xcex2-ketoesters, xcex2-aminocrotonates, uracil derivatives, dihydropyridine derivatives, sterically hindered phenols, sterically hindered amines, phosphites, polyols and hydrotalcites. It is also possible, advantageously, for the plasticisers according to the invention to be combined with known plasticisers such as dialkyl phthalates, dialkyl adipates, dialkyl azelates and dialkyl sebacates, alkylbenzyl phthalates, trialkyl trimellitates, triaryl phosphates, citric acid esters, alkyl benzoates and polyesters based on adipic acid or azelaic acid, and thus for an optimal combination to be achieved in terms of compatibility, renewability, degradability, and plasticising properties.
The derivatives according to the invention can be used for plasticising and/or solubilising any polymer systems, including thermoplasts (PVC etc.), rubbers, inks, coatings, adhesives, sealants. foams and thermosetting resins.
Examples of the use as plasticiser are given below. The plasticisers are used in a manner known for plasticisers and plasticising solvents, as described e.g. in: I. Skeist (ed.), Handbook of Adhesives. 3rd ed., Van Nostrand Reinhold, NY (1990), and H. F. Mark, Encyclopedia of polymer Science and Engineering, 2nd ed., NY (1985). Sealants: The derivatives of the invention can be used as a plasticiser in sealants and caulks, for example in a one or two-component polysulphide sealant or in acrylates or polysiloxanes or natural or synthetic rubbers. In addition to the plasticisers, other components may used in a sealant: epoxidised unsaturated oil (soy, fish, linseed oil), inorganic pigments, desiccants, fillers, and activators such as silica, calcium carbonate, titanium dioxide, lime, zeolites, and adhesion aids, such as organosilicon compounds, and aqueous or organic solvents).
Printing inks: The derivatives of the invention can be used as plasticiser or solvent in printing ink formulations for application in letterpress (relief), gravure (intaglio), offset lithography (planographic), screen (stencil), electrostatic (reprography) and jet (ink spray) printing. Suitable polymer systems for printing inks include acrylates, rosins, polyamides, polyesters, hydrocarbon resins, alkyd resins, nitrocellulose, cellulose acetates, etc.
Adhesives and coatings: The derivatives of the invention can be used as plasticisers in adhesives. Their function is to improve the flexibility, wetting properties and water resistance. The derivatives of the invention are applied as plasticiser for adhesives and sealants of the following classes: natural rubber; synthetic rubber, e.g. butyl, nitrile, neoprene, isoprene, styrene-butadiene rubber and copolymers thereof; carboxylated rubber and carboxyl functional polymers, e.g. and acrylic acid polymers and copolymers; phenolic and amino resin (e.g. urea, melamine); polysulphide resins and adhesives; epoxy resins and adhesives; polyurethanes and isocyanate-functional adhesives; polyvinyl alcohol and polyvinyl acetate and acetal adhesives; acrylate, cyanoacrylate and acrylic acid adhesives and their copolymers; polyester and polyamide; silicone adhesives The types of adhesives include: reactive one-and two component adhesives; hot-melt adhesives; delayed-tack adhesives; solution adhesives; in particular pressure-sensitive adhesives.
Rubbers and thermoplastic elastomers: The plasticisers of the invention can be used as plasticisers in cured or non-cured natural and synthetic rubbers, and in thermoplastic elastomers. These include all common rubbers, in particular acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), styrene butadiene rubber (SBR), polybutadiene (BR), 1 to 100 parts, in particular, 5-30 parts. The derivatives are used for decreasing the glass temperature of the rubber and for increasing tensile strength and strength on rupture. Thermosets: The plasticisers of the invention can be used as plasticisers in thermosetting resins (e.g. polyesters, amino resins) in order to improve the toughness and elongation. Foams: The derivatives of the invention can also be used as plasticisers in polymeric foams, in particular polyurethane, polyether and latex (natural or synthetic rubber) foams. They can be used to increase compression strength of the foam, refine the cell structure, improve its insulation resistance and increase its tenacity or other chemical, physical or mechanical properties.